It took 15 years to discover one of the most damaging cases of espionage in U.S. history. An inside look at the secret life, and final capture, of Robert Hanssen

"Eventually I would appreciate an escape plan. (Nothing lasts forever.)" --"B," November 1985

Those who betray must always fear betrayal. It happened to Robert Philip Hanssen a little after 8 p.m. on a Sunday night, just five weeks shy of his planned retirement from the spy game. Ten armed FBI agents shivered in the cold as they watched Hanssen walk up to a "dead drop" code-named Ellis, a spot under a bridge in a quiet suburban Virginia park where he hid a plastic garbage bag full of secret U.S. documents. As he emerged from the woods of Foxstone Park, the agents,...